F38
Linux e7.eyal.emu.id.au 6.5.8-200.fc38.x86_64 #1 SMP PREEMPT_DYNAMIC Fri Oct 20 
15:53:48 UTC 2023 x86_64 GNU/Linux

I am looking at issues with my system which is ATM degraded (6/7 raid6 devices).
I am waiting for a replacement disk from seagate RMA.

Unrelated, I am trying to copy a directory from an external USB3.0 HDD(ext4 on 
/sata) to a local RAID fs (ext4 on /data1).
I see rsync in top as:

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
 734489 root      20   0  122048  29392   2284 R  98.3   0.1  28:37.88 rsync

So high %CPU. This is pretty much constant.

I am also running iostat of both the source(sdh) and target(md127) devices, and 
it looks like this:

12:47:06 Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    
kB_read    kB_wrtn    kB_dscd
___
13:12:06 sdh               0.38         1.93         0.00         0.00        
116          0          0
13:13:06 sdh               0.30         1.87         0.00         0.00        
112          0          0
___
13:12:06 md127             4.12         0.00        16.47         0.00          
0        988          0
13:13:06 md127             1.90         0.00         7.60         0.00          
0        456          0

Note the very low kB_read/s. hdparm tests the external as 121.29 MB/s and the 
array as 748.18 MB/sec (tested now, during the rsync).

This also is at this slowness for the last hour, and earlier tests had it 
running like this for many hours.

Here is an idea of what it is doing:

$ sudo ps ax -o pid,wchan=WIDE-WCHAN-COLUMN -o times -o command | grep rsync
 734486 do_sys_poll              0 sudo rsync -aHSK --stats --progress 
--checksum-choice=none --no-compress -W /sata/backups/tapes 
/data1/no-backup/old-backups/
 734487 do_select               16 rsync -aHSK --stats --progress 
--checksum-choice=none --no-compress -W /sata/backups/tapes 
/data1/no-backup/old-backups/
 734488 do_select               14 rsync -aHSK --stats --progress 
--checksum-choice=none --no-compress -W /sata/backups/tapes 
/data1/no-backup/old-backups/
 734489 -                     2093 rsync -aHSK --stats --progress 
--checksum-choice=none --no-compress -W /sata/backups/tapes 
/data1/no-backup/old-backups/

It is clear that two threads are mostly idle and one is very busy.

Why does rsync use so much CPU? Am I using the wrong options?

TIA

--
Eyal at Home (fed...@eyal.emu.id.au)
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